Field of the Invention
The present invention relates to technologies for detecting touched positions and touchdown.
Description of the Related Art
Conventionally, arranging some devices on a screen as a projection target enables touch input when performing the touch input through an image projected by a projector. Japanese Patent Application Laid-Open Nos. 2004-272353 and 2001-43021 disclose techniques for coordinates input and touch determination, the techniques comprising: arranging means for projecting infrared rays and means for receiving the infrared rays on a screen; and detecting fingers interrupting the infrared rays by using these means so as to perform the coordinates input and the touch determination. Meanwhile, Japanese Patent Application Laid-Open Nos. 2001-236179, 2004-265185 and 2000-81950 disclose techniques of inputting indication through an image projected by a projector without arranging any device on a screen. Unfortunately, the techniques disclosed in these documents require a dedicated pointing device. The pointing device emits light or ultrasonic waves, which is detected in proximity to a projection area or at a position apart from the screen, thereby enabling coordinates input and touch determination.
A projector, which is regarded as one of display devices, has an advantage of capability of projection onto any place, in comparison with a flat panel type display device, e.g., a liquid crystal display device. The feature of “capability of projection onto any place” is incompatible with the requirement of “arranging some devices on a screen”, which hinders its convenience. Likewise, the feature of “capability of projection onto any place” is incompatible with the requirement of “a dedicated pointing device”, which also hinders its convenience. For compatibility therebetween, Japanese Patent Application Laid-Open No. 2011-118533 discloses a technique of touch input, the technique comprising detecting shadows of hands or fingers using a camera arranged on a side of a projector. The disclosed technique detects a touched position and determines a touchdown when a user touches a certain position on a projected image with a hand.
In the technique disclosed in Japanese Patent Application Laid-Open No. 2011-118533, however, the detection of the touched position and determination of the touchdown are performed based on a relationship between a real image of a hand illuminated with projection light and a shadow image of the hand generated by the projection light. If there is a black region in the projected image, no effective light beam can be obtained in the region using this technique, and consequently the shadow image and the real image cannot be sufficiently obtained. Accordingly, the touched position and touchdown cannot be correctly detected by the disclosed technique.
Thus, it is an object of the present invention to reliably obtain a shadow image and to correctly detect pertaining to a touch.